(1) Field of the Invention
The present invention relates to an improvement on an electrolytic corrosion resistant insulator for use in a direct current transmission line and the like.
(2) Description of the Prior Art
In order to prevent the electrolytic corrosion of the pin in an insulator due to electric current leakage and the resultant damage to an insulator in a DC transmission line, there has been used an electrolytic corrosion resistant insulator in which a sacrificial anode is projectingly provided around the outer periphery of the pin at an intermediate position thereof in the boundary with the cement, where the density of the current leakage is the largest. However, such an insulator has the problems that when the cement into which the pin is embedded is wetted under a severely contaminating environment and only the surface of the cement is half-dried under the influence of the wind or the like, the difference in electric resistance between the sacrificial anode and the pin body embedded in the cement becomes a minimum among the electric resistance between the insulator body and the pin, resulting in the leakage current to flow through the pin body so as to electrolytically corrode the pin. Furthermore, a large internal pressure stress is produced in the interior of the electric insulator by the rust formed through the electrolytic corrosion to thereby cause the electric insulator to break.